Doctrine of Equivalents in the USA - Is the Solution Crystal?

Eli Lilly and Co. v. Hospira, Inc. (US Fed. Cir. 2019)

Eli Lilly is the patent holder of a drug called pemetrexed (Lilly brand “Alimta”) that has been the subject of court proceedings in the UK, which we have reported previously. This case concerns a related issue during US proceedings in which the US Federal Circuit applied the doctrine of equivalents. Given the development of such a doctrine of equivalents in UK practice, we thought it would interesting to highlight the facts of this case also.

Doctrine of Equivalents in the USA - Is the Solution Crystal?

Eli Lilly is the patent holder of a drug called pemetrexed (Lilly brand "Alimta") that has been the subject of court proceedings in the UK, which we have reported previously.

This case concerns a related issue during US proceedings in which the US Federal Circuit applied the doctrine of equivalents. Given the development of such a doctrine of equivalents in UK practice, we thought it would interesting to highlight the facts of this case also.

Pemetrexed is approved in the US for the treatment of inoperable malignant pleural mesothelioma. It is an anti-folate, i.e. it blocks the uptake and binding of folic acid by cancers and their consequent growth.

The proceedings arose because generics companies Hospira and Dr. Reddy's Laboratories filed abbreviated new drug applications (ANDA) in the USA that Lilly alleges infringe US patent No. 7,772,209 ('209 patent).

Notably, this patent does not cover the drug itself but rather covers "a method for administering pemetrexed disodium to a patient in need thereof" ('209 patent, claim 1).

As in the UK and Italian proceedings we have previously reported, the crucial term at issue is "disodium". However the reasoning is different in this case.

In this case, a literal reading of claim 1 appears to mean the method is limited to administering disodium compositions which are, necessarily, crystalline. This is arguably in contrast to pemetrexed disodium dissolved in water. And this is what Hospira argued - effectively, a dissolved salt is no longer a salt and so the two forms of pemetrexed are not equivalent.

At first instance, the District Court found for the Patentee writing that:

"Administration of pemetrexed disodium […] refer[s] to a liquid administration of pemetrexed disodium […] accomplished by dissolving the solid compound pemetrexed disodium into solution."

Thus, the District Court found that there had been literal infringement of the '209 patent, i.e. crystalline pemetrexed disodium is equivalent to a solution of pemetrexed disodium.

However, on appeal the Federal Circuit reversed this Decision and found no literal infringement because, as argued by Hospira, a dissolved salt is no longer a disodium salt. The Federal Circuit stated that:

"A solution of pemetrexed and chloride anions and tromethamine and sodium cations cannot be deemed pemetrexed disodium simply because some assortment of the ions in the solution consists of pemetrexed and two sodium cations […] Once diluted the salt's crystalline structure dissolves, and the individual ions dissociate. In other words, pemetrexed disodium no longer exists once dissolved in solution, and, as a corollary, a different salt of pemetrexed dissolved in saline is not pemetrexed disodium."

Thus, there was no literal infringement.

However, the Federal Circuit invoked the Doctrine of Equivalents and produced a strong decision holding that the proposed generic solution of dissolved disodium pemetrexed is equivalent to the disodium pemetrexed salt itself. Therefore the proposed saline solution of pemetrexed infringes the '209 patent.

Thus, the District Court's judgement of infringement against Hospira and Dr. Reddy's Laboratories was confirmed despite the lack of literal infringement.

This case is a further example of the use of the doctrine of equivalents under US practice. The decision is not unexpected as there are few concepts in US patent law that have been so consistently supported by decisions of the US Supreme Court. The relatively recent "Festo VIII" decision of the US Supreme Court stated that "equivalents remain a firmly entrenched part of the settled rights protected by the patent" ( Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 733 (2002)). This is the most recent of a chain of consistent Supreme Court decisions that reach back to the middle of the 19th Century.

Thus this US decision provides a result similar to the "pemetrexed" cases in the UK and Italy that we have previously reported but reaches this conclusion by a slightly different (but dare we say, equivalent) route. Thus it appears that the doctrine of equivalents is a principle that is increasing its global reach and relevance to international patent practice.

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